Protective system



Dec. 13, 1927.

1,652,974 w. BRUCKEL PROTEQTIVE SYSTEM Filed April 22. 1925 t+ P1 ii 0 Q\ Q m R Inventor:

Waldemar Bruckel,

His Att Carney;

Patented Dec. 13, 1927.

WALDEMAR BnticKnL, or BERLIN, GERMANY,

ASSIGNOR To GENERAL ELECTRIC,

' COMPANY, A CORPORATION OF NEW YORK.

PROTECTIVE SYSTEM.

Application filed April 22, 1925, Serial No. 25,004, and in Germany May 30, 1924.

My invention relates to improvements in protective systems for electric circuits and morefiparticularly to improvements in protective systems for alternating Current circuits. -wherein,discriminating action is obtained by comparison of electric characteristics of a' circuit at different points thereof and an object of myinvention is to provide an improved discriminating? protective'system wherein the use ofpilotwires is eliminated. v.

My' invention. will; beybetter understood from the following description -taken' in.

connection with: they accompanying drawing and itsscope will be pointed out in the appended claims. Y

:The single figure ,of, the accompanying drawing. illustrates in a single line diagram for the sake of clearness anembodiment of my. invention as applied to two points of an alternating current circuit such 'as a power line conductor 1 which may extend bet-ween a plurality of interconnected generating and distributing stations, two of whichare illustrated asubusse's 2,:3, Three sections of the line 1 are shown, extending two from and one between theistations 2 and 3, the latter section being shown partly by a ,broken line to giwr a concept of distance between the stations. For controlling'the circuits of. the different sections at the ends thereof suitable circuit. interruptingmeans, such as circuit r breakers hand-5 on oppositevsid'es of the bus at station 2' and circuit breakers 6 and 7 on opposite sides of the'bus at station 3 may be provided so that,,0n the occurrence of a fault on. any, section such as the one between the or stations 2 and; 3, the section can be isolated without interrupting continuity of service 40 on the sound sections. {Although my invention is herein illustrated as applied tov a sectionalized circuit; such as a; power line feeder or the like, since it has a particular phase of utilitywhere distance between sta- (ions is involved, its application is not so.

limited as it is also'adapted to the discriminating protection of parallel lines and the like.

In accordance with my invention, I provide means, such as thermionic apparatus 8 at one point of the circuit, for transmitting :1 carrier wave of a predetermined frequency .aml for modulating the carrier wave in accordance with an electric characteristic of the circuit at the point. This characteristic 5 of the circuit maybe, forexample, the our rent inthe circuit or a current proportional thereto, which may be obtained from theoutputof suitable transforming means; such as a current transformer 9-" The carrier wave may be transmitted .through space withoutwires or as a carrier current over the line conductor 1 from the transmitterv 8 to means, such as athermionic receiver 10 located at another point of the circuitfor demodulating the modulated carrier ,wave; transmitted by the transmitter-8. For con? trolling the circuit breaker 6 selectively in accordance with the demodulated carrier: Wave and an electric characteristicof the cir cuit at the location; of'the receiver 10, I pro-; i vide means such as a{ relay l -1 which, as

shown, is arranged to be actuated when the;

currents-in the-circuit atthe ends ofgthee section between the 'stations32 and; 3 ;exce ed a definite difference in phase and/ormagniv tude, that is, in accordance with the resultant of the demodulatedcarrier current andthe current inthe circuit at'station 3 01' a cur rent proportional thereto as providedrby a 30 current transformer 90. In a similar manner,".the station: 3, is pro,-, vided with a transmitter 12 adaptedto transmit a carriervwave having afrequency diffen ing from that transmitted by the transmitter as 8 and modulated in accordancewiththe curs, rent. in the circuit. at station 3, that is by the potential across the secondary. of the current; transformer Also station 2 is provided, with a receiver 13 adaptedito demodulate the. 90 carrier wave transmitted. by the transmitterj 12.] For controlling the circuitbreaker 5, a relay 110,.arranged to be actuated in accordance with the resultant of this demodulated carrier wave andthe current in the secondary of the current transformer 9 is rovided. Similar apparatus may be provided for each circuit breaker in the conductor 1 at every station sothat upon the occurrence of a fault in any section, the circuit breakers controllingthat section are opened and the section thus isolated. e

The transmitters8 and 12 may be of any suitable type and are herein shown as high frequency devices of a type well known to the art; They comprisean oscillator element including an oscillator thermionic device or tube 14 and an oscillator circuit 15, the oscillations of which are modulated by a modulator "element, including a modulator thermionic device or tube 16. The oscillator circuit .15, coupled ,to the I conductor 1 throughafi' emperor coupling coil 17 and the high frequency modulated oscillation or carrier wave is transmitted in a mannerwell known to the art over a suitably tuned stop circuit or wave .trap;-18;and a. condenser L9 to the conductor 1. The receivers 10 and 13 may be'of 'any suitable'type and are h'erein shown as hi'gh frequency devices of a type 15 well known to the' art. They comprise a receiving circuit and a reotifier or demo'dulator thei mioiiic device ortube 21-, the

v output bfwliich ma'y be suitably amplified as 'is well known to the art; The receiving 20 circuit 20; is-coupled to 'the conductor 1 throu'gh a'ii input or coupling coil 22 which is energized hy-the -m0dulated= carrier current'transmitted over the condensers 19 and a suitably tuned stop =circuit or wave trap 23. 25 The-'stop-circuits fl aiid 23a't the respective stations prevent interference between the transmitier and receiver atjthe station by blocking the I highfrequency oscillations of the" transmitter at" the station from "the receiver-at the same station,- while permitting the passage of the-high frequency oscillations from fth e" transmitter 8 or 12 at "one station to' th receiver- 1'0 'or 13' "respectively at-the otherstationi The receivers 10 and 13 are tuned-to the frequeneies 'of the carrier waves transmitted by the transmitters 8 {and' 12' re'spe'cti'vely"and in view of inherent variationsgn line conditions, such; as length of section,"impedafice and like factor'sl' the difi'er- 40 cut circuit elements oftli'etrarismitters and receivers maybe made adjustable *to secure. the-desired tuning e For' modulating the carrier wave of the oscillator circuit in accordance with the output of thesecondary'of the current transformer at the station, the circuit of the sec ondary-isprovided with suitable means, such as "a'resista-nce 24 which is also included in the grid'circuit of the modulator tube 16. Consequently, the potential; on the grid will vary in accordance with the'current in the cireuitl at the-station; The secondary circuit'also includes a winding 25 of difi'erentially responsive means comprisinga transf6rmer'26Q In order that the transmitter and receiver at a station may be normally inactive, the secondary circuit may also include suitable electror'esponsive means, such as an overcurrent relay '27 arranged normally to complete a shunt circuit across the secondary of the'eurrent transformer through contacts 25 and upon'the occurrence of a predetermined current in the circuit 1 to open the shunt 66 circuit and close the circuit of the filament up and stay up while the current remains at such prcdctermii'ied value.

The output or modulated carrier wave of the transmitter at one station as rectified or demodulated and amplified, if desired, by the receiver at the adjacent station, and the current at the adjacent station are correlated by the transformer 26. The demodulated carrier current may first be transformed by an intermediate transformer 32 having a winding in the plate or output circuit of the receiver and a winding in circuit with a winding 33 on the transformer 26 arranged differentially with respect to the winding 25. The purpose of the transformer 32 is to obtain better balance between the impedance of the receiver output circuit and the load circuit which includes the winding 33, that is, to match the tube impedanc with the load impedance.

The windings 25 and 33 of the transformer 26 are arranged for opposing magnetomotive forces so long as the currents at the stations are substantially in phase and therefore a secondary winding 34 normally has noelectromotive force induced therein unless the current at one station exceeds that at the other or differs in phase lherefron'i. The secondary winding 34 has in circuit therewith the winding of the relay 11 or which is arranged to control the circuit breaker at the station through its trip coil 35.

Assuming normal line conditions, then if the overcurrent relays 27 are used, neither of the transmitters 8 or 12 nor the receivers 10 or 13 will be operating. Upon the occurrence of an abnormal circuit condition causing a predetermined current at the stations, the relays 27 will operate and thus efiect the operation of the transmitters and receivers. If the abnormal circuit condition is due to a through fault, that is, a fault outside of the section of the circuit 1 between the stations 2 and 3, then the windings 25 and will be energized substantially alike and therefore produce no currentto cause the operation of the relays 11 and 110. If. however, the fault is within the section and assuming that the system of which the circuit 1 is a part is such that the fault may be fed from each end, that is, from stations 2 and 3, then the windings 25 and 33 assist. since the currents at the stations now diil'e': in phase and may also differ in magnitude. The resultant magnetomotive force of tllGl-U windings now induces sufiicient electronic tive force in the windings 34 of the transloo nesaova' may' 'ber employed. 1 c Those' skilled in I the art will appreciate that my invention is susceptibleto numerous modifications, and accordingly it is not desiredthat' it belimitedto the-particular ar rangement' and apparatus 1 herein described. It therefore, :aimed-;in the. appended: claims to cover all modifications which are within the spirit and scope of. my invention. What li'iclaim asaanewv and desire to secure byzLetters Patentyo'f the United States, is

a) 11$ aAmprotective system for a an electric (fir-n1 cult comprising means at one point of the circuit for transmitting a carrier wave of-"a predetermined frequency and for inodulat ing' the; carriermwave in accordance with an and s an: electric characteristic of the circuit atisaid other pointi .3 2 .-.=A ipro tective system for; an electric: circuitucomprising :means at'i one: point of the circuit AfOra transmitting a carrier. wave of: apredeterrnined frequency-and for modulat-r ing the carrier wave in accordance with anelectrica'characteristicxof the circuit at said point imea'ns ati another-point of the circuit forf'demodulating said carrier wave, and

carrierwwave and -.the electric characteristic oflthe' circuit' at said otherpoint correspond ing toi the -electricwcharacteristic1 in faccord ance .with'rwhich the: carrier: wave: is m0du-,-

between the currentsiatfthei-endsiof the seclatedd ed? yr-1;!

13; A protective" sy cuitl'comprisingl means I at one; point of:-tl1e circuit.for transmittingl a carrier wave of; a: predetermined 7 frequency :and for modulat-w ingthelcarrierwave in accordance :with the intensity ofithecurrent in the circuit at said' point; receiving "means, at another, point of; thecircuits;adapted. to; demodulate said carrierwWaVeQ-cand means: for v controlling the circuit' int'accordance with-the resultant of thez-demodula'tedwave and. the intensity of; the currentiin the-circuit at. said other point. v

41 A protective system for" an alternating.

current circuitcomprising; transforming means associated with the circuit at separateadaptedto demodulate said carrier wave,'

andmeans for controlling thecircuit. at

- said other point in accordance with the re tem for an electric cir--,

sultant of the demodulated: wave and the output of the transforming: meansfat-said other point. I w ='i= 5. In a 'prote'ctive system of-'.-'the -;t'ype wherein circuit r controlling 2 meansare 1 controlled in accordance with theJdifl'ereDCebem tween the currents at the ends off a sec? tion of an electric circuit means fOY'CQDct trolling the circuit controlling-means a'tfones end of the section comprising azi-deviceiree 7e: sponsive to the current; in the CiICllitzfittthfitend of the section and means for aflectingi said device in accordance with the current; in the circuit at theother end offthe section. comprising means for transmitting between; the ends of the sectionla carrier-wave mod-i ulated in accordance with the current ini'thei circuit at the other end of the section: a

6. In a protective systemof the type: wherein circuit controllingimean's are con- S51 trolled in accordance with the difl'erence be-V: tween the currents at the endszofaasection of: an electric circuit, means {for controlling the; circuit controlling means-rat iOIlBEBB-(i otlithe section comprising;aitransformerrilraving a winding connected to be -ene'rgiz'ediirtzaccordrf ance with the current atithat endmff; the; 5801i tion and a 1 cooperating jwindihg-Jarranged; to be energized inacc ordanc'e wifthsthe curia rent at the other end'Io'fit-hei sectionguandflii means for efi'ecting' thereneigizationqoflsaid! cooperating windingv in accordance; {with the current at thel'otherfend ofatheise'ctiongcdmv-f prising means 'for: transmitting,:fromzsaidr other end a carrier wave modulat'jedrgindacez cordance with the currentcinzzthfiac rpuitrafi that end. 1'. ''t. ;=.i'; gi i1 iii (T-In a protective system' 'ofie'theehypfii wherein circuit controllingemeansdata: each: end of a section of.anb electriccicireuit ,8116: controlled in accordance withnthe'rdifierenoers the respective; end: comprising, a t 1;ansvormer=; 1 U) in accordance: with the;current in thecircuiti I at the end of the section at 'gWhiCh; the-,trans-f; former is located and acooperating winding means for transmitting a carrier-wavemodu; lated in accordance witliztheourrfinfaiin the; section at the respective end;thefj-transmi tii ting means at thetwo ends beingzarranged,

to transmit carrieri Waves ;,-.having different predetermined freq,uencies; and; .receiving; means for effecting the energizationt of the; cooperating winding of the transformer at one end of the sectionin accordance with, the modulated carrier wave; transmitted from the other end of the section. p

8. In a protective system oftheytype wherein circuit controlling-means at;;each-- end of a section of an electric circuit are controlled in accordancewith v thedi fi'ference between the currents at the ends of the sec 130 tion, means at each end of the section for controlling the circuit controlling means at the respective end comprising a transformer having a winding connected to be energize-l in accordance with the current in the circuit at the end of the section at which the transformer is located and a cooperating winding, means for transmitting a carrier wave modulated in accordance with the current in the section at the respective end, the transmitting means at the. two ends being arranged to transmit carrier waves having. different predetermined frequencies, receiving means for effecting the energization of the cooperating Winding of the transformer at one end of the section in accordance with the modulated carrier wave transmitted ffrom the other end of the section, and means at each end of the section for preventing interference between the transmitting and receiving means at the respective end and for permitting passage of the modulated carrier wave transmitted from one end to the receiving means at the other end.

9. A protective system, for an alternating current circuit comprising transforming means associated with the circuit at sepaiate pointscthereof, transmittingvmeans at one'of said points adapted to transmit a carrier wave modulated in accordance with the output ofi the" transforming means at said point, receiving means at another of said points adapted to'demodulate said carrier wave, and means for correlatin the demodulatedwave and the output of the transforming means atsaid other point comprising electroresponsive circuit controlling means arrangedito-be controlled in accordance-with theresultant of the demodulated wave and: the z'ou-tputifi of the transforming means at saidl'other point. c v- "10. A} protective system for an electric ciicuit-comprisin normally inactive means at one'point 'oft e' circuitfor transmitting a carrier-wave of a, predetermined frequency and for'modulating' the carrier wave in ac-' cordance{-wi th{anelectric characteristic of the circuit atsaid point, means for effecting operation of said normally inactive means on the occurcnce of an abnormal circuit condition, means at another point of'the circuit for demodulating said carrier wave, and circuit controlling means arranged to be controlled by, said demodulated carrier wave and an electric characteristic of the circuit at said other point.

11. A protective system for an electric ciicuit'comprisin normally inactive means at one point of the circuit for transmitting a carrier wave of a predetermined frequency and for modulating the carrier wave in accordance with an electric characteristic of the circuit at said point, normally inactive means at another point of the circuit for deinodulating said carrier wave, means for effecting operation of both of said normally inactive means on the occurrence of a fault on the circuit, and circuit controlling means arranged to be controlled by said demodulated carrier wave and an electric characteristic of the circuit at said other point.

12. A protective system for an alternating current circuit comprising current transformers associated with the circuit at separate points thereof, normall inactive transmitting means at one of sai points adapted to transmita carrier current modulated in accordance with the potential across thecurrent circuit comprising current trans-.-.

formers associated with thecircuit at ;sepa

rate points thereof, normallyinactive trans-- mitting means at one of said -pointsadapted:

to transmit a carrier current having-awpre-z determined frequency and modulated in accordance with the potential: across the secondary of the currentxtransformer at said point, normally inactive'a -receiving means at another ofsaid. pointsadapted to;

demodulate said carrier: current, over-current relays at'said'pointsrespectively ar-- ranged toeffect operationtofi the;tra.nsmitting and the receiving:' 'mea'nswliponi' the: oc-

currence of 'a; predetermined currentin the circuit and means for controlhng the circuit' at said other'point in=accordancew:ith the difference between the idemodnlated" carrier current and the output of the secondary of the current transformer at said-other point.

"14. A protective system for arr-alternat ing current circuit comprising. current transformers associated- 'with" the circuit at separate points'v thereof, :transmitting means at one of said points ad'apted to transmit a carrier current modulated-in accordance with the potential across the secondary of the current transformer atfsaid point, receiving means at another of said. points adapted to' demodulate said carrier current,

and means for controlling the circuit at said other point in accordance with the re sultant of the demodulated carrier current and the output of the secondary-of the current transformer at said other point.

15. A protective system for an alternating current circuit comprising current transformers associated with the circuit at separate points thereof, transmitting meansat inactive receiving.

one of said points adapted to transmit a carrier current having a predetermined frequency and modulated in accordance with the potential across the secondary of the current transformer at said point, receiving means at another of said points adapted to demodulate said carrier current, and means for correlating the demodulated carrier current and the output of the secondary of the current transformer at said other point comprising electroresponsive circuit controlling means arranged to be controlled in accordance with the resultant of the demodulated carrier current and the output of the secondary of the current transformer at said other point.

16. A differential protective system for an alternating current circuit comprising current transformers associated with the circuit at separate points thereof and means for controlling the circuit in accordance with the difference between the currents in the circuit at said points comprising a normally inactive transmitter at one of said points adapted to transmit a carrier current avlng a predetermined frequency and modulated in accordance with the output of the secondary of the current transformer at said point, a normally inactive receiver at another of said points adapted to demodulate said carrier current, an over-current relay at each of said points respectively arranged to effect operation of the transmitter and receiver upon the occurrence of a predetermined current in the circuit at said points, and a relay arranged to be controlled in accordance with the difference between said demodulated carrier current and the output of the secondary of the current transformer at said other point.

In witness whereof, I have hereunto set my hand this 4th day of April, 1925.

WALDEMAR BRUCKEL. 

